AFGL 5173

Lying at a distance of 6500 light years, AFGL 5173 (also known as RAFGL 5173 and G192.16-3.82) is a compact HII region with the reflection nebula Parsamian 4. It's most striking feature are a pair of Herbig Haro objects HH 396 and HH 397 that represent a giant Herbig Haro outflow with a length of 18 arcminutes or 32 light years! This is one of the largest and brightest known Herbig Haro complexes and is powered by a moderately massive protostar.

The HH 396-7 outflow is comprised of multiple Herbig Haro objects with HH 396 to the right and HH 397 to the left. They are the result of jets from a protostar and the optically visible nebulosity is produced either when fast moving ejecta overtake slow moving ejecta or when the ejected material impacts ambient gas in the surrounding area. This produces shocks and the energy generated ionizes the ejected gas and makes it glow in both optical and infrared wavelengths. The structure of the bipolar outflow indicates multiple episodes of ejecta events.

The protostar responsible for driving the HH 396-7 outflow isn't visible optically and is shrouded behind a veil of dust. Studies by professional astronomers with radio telescopes have detected a rotating circumstellar disk around this protostar. Usually outflows and Herbig Haro objects are a consequence of excess material falling from the disk onto the star. The age of the outflow has been estimated to be between 10,000 and 100,000 years. In the southern half of this deep image, extremely faint emission nebulosity is also visible, which is likely to be uncatalogued and previously unknown.